function Validity(){
    var uname=theform.uname.value;
    var pwd=theform.pwd.value;
	if (uname==""){
		alert("请输入用户名！");
		 return false;
	}
	if (pwd==""){
		alert("请输入密码！");
		return false;
	}
	var check1=	checkno(uname);
	if(check1){
	    return true;
	}else{
	      return false;
	}
}

function checkno(code){
          var   strangCode   =   "~!@%^&*();'\"?><[]{}\\|,:/=+—“”‘";  
          var   temp;  
          for   (var  i  =  0;   i<code.length;   i++   )  
         {  
                 temp   =   code.substring(i,i+1);  
                if   (strangCode.indexOf(temp)   !=-1)  
                {  
                         alert("文本框中含有非法字符[   "   +   temp   +   "   ]！");  
                          return  false;  
                }  
          }  
         return   true; 
  }